temp.cpp

int largestArea(int arr[], int len)  
{  
    int area[len]; //initialize it to 0  
    int n, i, t;  
    stack<int> St;  //include stack for using this #include<stack>  
    bool done;  

    for (i=0; i<len; i++)  
    {  
        while (!St.empty())  
        {  
            if(arr[i] <= arr[St.top()])  
            {  
                St.pop();  
            }  
            else  
                break;  
        }  
        if(St.empty())  
            t = -1;  
        else  
            t = St.top();  
        //Calculating Li  
        area[i] = i - t - 1;  
        St.push(i);  
    }  

    //clearing stack for finding Ri  
    while (!St.empty())  
        St.pop();  

    for (i=len-1; i>=0; i--)  
    {  
        while (!St.empty())  
        {  
            if(arr[i] <= arr[St.top()])  
            {  
                St.pop();  
            }  
            else  
                break;  
        }  
        if(St.empty())  
            t = len;  
        else  
            t = St.top();  
        //calculating Ri, after this step area[i] = Li + Ri  
        area[i] += t - i -1;  
        St.push(i);  
    }  

    int max = 0;  
    //Calculating Area[i] and find max Area  
    for (i=0; i<len; i++)  
    {  
        area[i] = arr[i] * (area[i] + 1);  
        if (area[i] > max)  
            max = area[i];  
    }  

    return max;  
}